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A Test Bed to Examine Helmet Fit and Retention and Biomechanical Measures of Head and Neck Injury in Simulated Impact
Published on: September 21, 2017
Pediatric occupant human body model kinematic and kinetic response variation to changes in seating posture in
Jalaj Maheshwari1, Shreyas Sarfare1, Clayton Falciani1,2
1Center for Injury Research and Prevention, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
Insights
Pre-crash automatic emergency braking (AEB) significantly reduces injury risks for children in booster seats during frontal impacts. Naturalistic seating postures, however, greatly influence injury exposure, highlighting the need for robust restraint system designs.
Area of Science:
- Biomechanics
- Occupant Protection
- Vehicle Safety
Background:
- Child restraint systems (CRSs) are crucial for protecting children in vehicles.
- Understanding the impact of naturalistic seating postures on CRS effectiveness is vital.
- The role of pre-crash automatic emergency braking (AEB) in mitigating crash forces for children needs further investigation.
Purpose of the Study:
- To quantify the kinematics of children in booster CRSs during frontal impacts.
- To evaluate the influence of various naturalistic seating postures on injury metrics.
- To assess the impact of pre-crash AEB on child occupant protection.
Main Methods:
- Utilized PIPER pediatric human body models (6YO and 10YO) in booster seats (LBB, HBB) and a NoCRS condition.
- Simulated four naturalistic seating postures plus a baseline in a 2012 Toyota Camry FE model.
- Exposed models to frontal rigid-barrier impacts at 35 MPH, with and without pre-crash AEB, using LS-DYNA.
Main Results:
- Forward-leaning postures increased head excursion; lap belt slippage occurred in pre-submarining positions.
- No head contact was observed in any simulated scenario.
- Cases with pre-crash AEB demonstrated lower injury metrics (HIC15, head acceleration, neck forces/moments) compared to non-AEB cases.
Conclusions:
- Pre-crash AEB effectively reduces impact severity by limiting occupant travel distance and initiating earlier ride-down.
- Naturalistic seating postures significantly affect injury risk, necessitating consideration in CRS design.
- Vehicle and CRS designs must account for diverse seating postures to ensure comprehensive occupant protection.
Objective:
The study quantifies the kinematics of children in booster child restraint systems (CRSs) in various naturalistic seating postures exposed to frontal impacts in a full-vehicle environment, with and without the application of pre-crash automatic emergency braking.
Methods:
The PIPER 6YO and 10YO pediatric human body models were positioned in CRSs. The 6YO was restrained on a lowback (LBB) and highback (HBB) booster, while the 10YO was positioned on an LBB and in a NoCRS condition. All simulations used the 3-point seatbelt. The child models were pre-positioned (gravity settled, seatbelt tensioned) in four naturalistic seating postures: leaning-forward, leaning-forward-inward, leaning-forward-outward, and a pre-submarining position, along with a baseline reference seating position. A 2012 Toyota Camry finite element (FE) model was used as the vehicle environment. A standard 3-point lap-shoulder belt system was modeled to restrain the child and CRS in the left-rear vehicle seat. Two vehicle impact cases were considered: with and without a pre-crash AEB. For with-AEB cases, a pre-crash phase was run to incorporate postural changes due to the application of AEB. All seating positions were ultimately subjected to a full-frontal rigid-barrier impact at 35 MPH. A total of 40 conditions were simulated in LS-DYNA.
Results:
Injury metrics varied widely for both occupants. Shoulder belt slippage was observed for the 6YO leaning-forward-inward on HBB. No head contact was observed for any simulated cases. Forward-leaning and forward-inward-leaning postures generally had greater head excursion across all seating postures. The lap belt rode over the pelvis for pre-submarining postures. Injury metrics for cases with pre-crash AEB were lower compared to their corresponding without-AEB cases. HIC15, head acceleration, upper neck tension force, and upper neck flexion moment were similar or lower for with-AEB scenarios.
Conclusions:
Pre-crash AEB reduces the effect of the impact despite the same collision speed as cases without-AEB. This is primarily due to the limited travel distance of the occupant, thus, starting an earlier ride-down during the crash. Moreover, different initial seating postures lead to a wide range of injury exposures. Vehicle and child restraint design should incorporate these seating postures to ensure robust protection of the occupant in a crash.
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